Platinum itself has a rather plain silver colour and, in consequence, is not considered to be particularly appealing for use in the jewellery trade. On the other hand, certain platinum intermetallic compounds, particularly those with aluminium, do have colours different from that of the constituent metals and, in particular, the intermetallic compound PtAl.sub.2 has a bright yellow colour.
However, such a colour does not necessarily render platinum, in this form, attractive for use in the jewellery trade as the yellow colour is not particularly distinctive over and above that of various gold alloys which are substantially more easy to work and form into jewellery whereas the platinum/aluminium intermetallic compounds are hard and brittle and not easy to form into attractive parts of articles of jewellery.
Some attention has been given to intermatallic compounds, that provide colour. Attention has thus been given in a number of publications to intermetallic compounds of gold and aluminium.
Regarding the physical properties of intermetallic compounds, European Patent Application No. 87810140 claims to provide an expedient for obtaining more workable intermetallic compounds from a physical point of view. This patent specification embraces an enormous range of possible compounds, both with and without precious metals. It fails, however, to teach any particularly useful platinum based compounds from a colour point of view.
It is the object of this invention to provide intermetallic compounds of platinum and aluminium which have the colour thereof modified to render them more attractive and aesthetically appealing for use as component parts of articles of jewellery.